Anchoring Ultrafine ZnFe₂O₄/C Nanoparticles on 3D ZnFe₂O₄ Nanoflakes for Boosting Cycle Stability and Energy Density of Flexible Asymmetric Supercapacitor

Abstract

Heterostructure-based metal oxide thin films are recognized as the leading material for new generation, high-performance, stable, and flexible supercapacitors. However, morphologies, like nanoflakes, nanotubes, nanorods, and so forth, have been found to suffer from issues related to poor cycle stability and energy density. Thus, to circumvent these problems, herein, we have developed a low-cost, high surface area, and environmentally benign self-assembled ZnFeO nanoflake@ZnFeO/C nanoparticle heterostructure electrode via anchoring ZnFeO and carbon nanoparticles using an in situ biomediated green rotational chemical bath deposition approach for the first time. The synthesized ZnFeO nanoflake@ZnFeO/C nanoparticle heterostructure thin films demonstrate an excellent specific capacitance of 1884 F g at a current density of 5 mA cm. Additionally, all solid-state flexible asymmetric supercapacitor devices were designed on the basis of ZnFeO nanoflake@ZnFeO/C nanoparticle heterostructures as the negative electrode and reduced graphene oxide and energy density of 81 Wh kg at a power density of 3.9 kW kg. Similarly, the asymmetric device exhibits ultralong cycle stability of 35 000 cycles by losing only 2% capacitance. The excellent performance of the device is attributed to the self-assembled organization of the heterostructures. Moreover, the in situ biomediated green strategy is also applicable for the synthesis of other metal oxide and carbon-based heterostructure electrodes.

Utilizing Waste Thermocol Sheets and Rusted Iron Wires to Fabricate Carbon–Fe3O4 Nanocomposite‐Based Supercapacitors: Turning Wastes into Value‐Added Materials

“…[30] Furthermore, aw eightl oss of 2.5 %within 150-350 8Cisdue to the decomposition of organic matter and ammonium complexes. [31] The carbon (3.87 %) and [32] There is no significant peak of graphitic carbon at 2q = 25.58 in the CÀ Fe 3 O 4 composite, which indicates the primary amorphous disordered structure of the carbon microparticles. [31] The carbon (3.87 %) and [32] There is no significant peak of graphitic carbon at 2q = 25.58 in the CÀ Fe 3 O 4 composite, which indicates the primary amorphous disordered structure of the carbon microparticles.…”

“…01-075-0449 (for Fe 3 O 4 ), as shown in Figure2b. [31] In particular,b ands above 600 cm À1 (606 and 664 cm À1 )c orrespond to the vibrations of Fe 2 + ÀO( FeO 4 units)i nt etrahedral sites, which have 2A 1g symmetry. The Raman spectrum( Figure 2c)o fp ure Fe 3 O 4 shows variousv ibrational modes within the wavenumberr ange of 200-700cm À1 ,w hich confirmst he formation of the spinel cubic phase.…”

“…For comparison, the XRD pattern of the pure carbon is presented in Figure S2 in the Supporting Information, in whicht here is only aw eak, broad peak centered at aroundat2 5.08,w hich supports the predominantly amorphous nature of carbon.F igure 2c shows comparativeR aman spectra of pure Fe 3 O 4 ,c arbon,a nd the CÀFe 3 O 4 composite. [31] The other bandsa t2 72, 292, 401, and 501 cm À1 are due to the vibrations of Fe 3 + ÀO( FeO 6 units) in octahedral sites, which are considered to have 3T 2g and E g symmetry.O no ther hand, the Raman spectrum of the CÀFe 3 O 4 composite reveals that, alongw ith Fe 3 O 4 vibrational modes,a na dditional broad band appears at 1298 cm À1 ,w hich is attributed to amorphous carbon. [31] In particular,b ands above 600 cm À1 (606 and 664 cm À1 )c orrespond to the vibrations of Fe 2 + ÀO( FeO 4 units)i nt etrahedral sites, which have 2A 1g symmetry.…”

“…The capacitive behavior of the CÀFe 3 O 4 composite can also be provenb yi ts triangle-like GCD curves (Figure 4b). [31] The small asymmetry is caused by the pseudocapacitance of Fe 3 O 4 . The specific capacitance of the CÀFe 3 O 4 composite, calculated from the GCD results, is 1375 Fg À1 at ac urrent density of 1Ag À1 (Figure 4c).…”

“…The Ni(OH) 2 -CNT electrode was synthesized according to aw et chemical route previously reported. [31] Finally the electrodes were pressed together under ap ressure of 1MPa for 5min, and sealed with plastic wrap to assemble the solid-state SC. [31] Afterwards, carbon paper electrodes loaded with the prescribed active materials (both negative and positive electrodes) and the separator were immersed in freshly prepared PVA-KOH gel electrolyte for 10 min and then solidified in air for 30 min.…”